The present invention relates to an improved self-locking fastening device having toothed engaging surfaces, and more particularly to improved fastening devices of the type including bolts, nuts and the like having lower engaging surface projections with teeth constructed to afford resistance to loosening of the fastening device, after being brought into pressure engagement with an adjacent surface of a workpiece by the tightening of the fastening device.
An object of the present invention is to provide an improved self-locking fastening device of the nut-type or bolt-type having a toothed engaging surface such that the torque required to loosen the fastening device greatly exceeds the torque required for tightening the fastening device.
Another object of the present invention is to provide such an improved fastening device with an engaging surface having ratchet-like projections in the form of double edges, whereby when the fastening device is turned in a loosening direction an adjacent workpiece surface is cut by the projections and engaged with the latter without abrasion or injury of the points of the projections, thereby obtaining a locking action by the fastening device.
Still another object of the present invention is to provide an integrally formed threaded fastening device having an engaging surface provided with a number of ratchet-like projections including some projections positioned relatively adjacent an outer periphery of the engaging surface and other projections positioned relatively adjacent an inner periphery of the engaging surface. Those projections positioned relatively adjacent the outer periphery of the engaging surface have a construction sufficient to bear a larger portion of the torque load than those projections positioned relatively adjacent the inner periphery of the engaging surface. All of the projections on the engaging surface are capable of engaging with an adjacent workpiece when the fastening device is rotated in a loosening direction.
An even still further object of the present invention is to provide a unique construction of the toothed engaging surface of the fastening device to provide higher release torque to application torque ratio characteristics then generally known lock-nut or bolt-type devices.